Time-tracking for clustered demodulation elements in a spread spectrum system

Abstract

An apparatus, such as a subscriber unit or a base station within a spread spectrum communication system, provides advanced control over the time-tracking of demodulation elements when unresolvable multipath situations arise. The apparatus provides merge protection that prevents clustered demodulation elements from contracting beyond a minimum time span. In addition, the apparatus provides a master/slave feature for synchronizing the time-tracking of the demodulation elements when clustered around a multipath signal.

1. A method comprising:
 determining whether a time tracking command would cause any time separation between a master demodulation element or any slave demodulation elements and a set of demodulation elements to decrease below a threshold; 
 determining whether the time tracking command is destined for the master demodulation element, associated with corresponding slave demodulation elements, or for one of the slave demodulation elements; 
 synchronously adjusting time offsets of the corresponding slave demodulation elements with the time offset of the master demodulation element responsive to receiving the time tracking command when the time tracking command is destined for the master demodulation element; and 
 filtering the time tracking command to prevent the time tracking command from being issued to the one of the slave demodulation elements when the time tracking command is destined for the one of the slave demodulation elements. 
 
   
   
     2. The method of  claim 1 , further comprising:
 intercepting the time-tracking command for adjusting a time offset of the master demodulation element; and 
 identifying any slave demodulation elements assigned to the master demodulation element. 
 
   
   
     3. The method of  claim 1 , further comprising:
 identifying the set of demodulation elements assigned to a same transmitter as the master demodulation element, and 
 determining whether application of the command would cause any time separation between the set of demodulation elements to decrease and to have a resultant time separation below the threshold. 
 
   
   
     4. The method of  claim 1 , wherein synchronously adjusting the time offsets of the master demodulation element and the corresponding slave demodulation elements comprises:
 forwarding the command to the master demodulation element and the corresponding slave demodulation elements when the time separation is equal to or exceed the threshold; and 
 filtering the command when the time separation is less than the threshold. 
 
   
   
     5. The method of  claim 1 , wherein synchronously adjusting time offsets of the master demodulation element and the slave demodulation elements based on the determination comprises synchronously adjusting the time offsets for the master demodulation element and the slave demodulation elements by substantially equal amounts. 
   
   
     6. The method of  claim 4 , wherein issuing the command comprises simultaneously issuing the command to the master demodulation element and the slave demodulation elements. 
   
   
     7. The method of  claim 1 , wherein the master, slave and set of demodulation elements demodulate the spread spectrum signal at a chip rate, and further wherein the threshold is within the range of 1/4 of a chip in time to two chips in time. 
   
   
     8. The method of  claim 1 , wherein adjusting the time offsets comprises issuing one of an advance or retard request. 
   
   
     9. A method comprising:
 calculating a time-tracking adjustment for a target demodulation element of a plurality of demodulation elements for demodulating a spread spectrum signal; and 
 synchronously adjusting a time offset of the target demodulation element and a time offset of at least one other of the demodulation elements, associated with the target demodulation element, based on the calculated time-tracking adjustment when the calculated time tracking command is destined for the target demodulation element; and 
 filtering the calculated time tracking command to prevent the calculated time tracking command from being issued to the at least one other of the demodulation elements when the calculated time tracking command is destined for the at least one other of the demodulation elements. 
 
   
   
     10. The method of  claim 9 , further comprising synchronously adjusting the time offset for the target demodulation element and the time offset of the other of the demodulation element by substantially equal amounts. 
   
   
     11. The method of  claim 9 , further comprising:
 intercepting a command to adjust the offset of the target demodulation element; and 
 issuing the command to the target demodulation element and the other demodulation element. 
 
   
   
     12. The method of  claim 11 , wherein issuing the command to the other demodulation element comprises issuing the command to the other demodulation element when the other demodulation element is designated as a slave to the target demodulation element. 
   
   
     13. The method of  claim 9 , wherein the time-tracking adjustment comprises one of an advance or retard request. 
   
   
     14. An apparatus comprising:
 means for determining whether a time tracking command would cause any time separation between a master demodulation element or any slave demodulation elements and a set of demodulation elements to decrease below a threshold; 
 means for determining whether the time tracking command is destined for the master demodulation element, associated with corresponding slave demodulation elements, or for one of the slave demodulation elements; 
 means for synchronously adjusting time offsets of the corresponding slave demodulation elements with the time offset of the master demodulation element responsive to receiving the time tracking command when the time tracking command is destined for the master demodulation element; and 
 means for filtering the time tracking command to prevent the time tracking command from being issued to the one of the slave demodulation elements when the time tracking command is destined for the one of the slave demodulation elements. 
 
   
   
     15. The apparatus of  claim 14 , further comprising:
 means for intercepting the time-tracking command for adjusting a time offset of the master demodulation element; and 
 means for identifying any slave demodulation elements assigned to the master demodulation element. 
 
   
   
     16. The apparatus of  claim 14 , further comprising:
 means for identifying the set of demodulation elements assigned to a same transmitter as the master demodulation element, and 
 means for determining whether application of the command would cause any time separation between the set of demodulation elements to decrease and to have a resultant time separation below the threshold. 
 
   
   
     17. The apparatus of  claim 14 , further comprising:
 means for forwarding the command to the master demodulation element and the corresponding slave demodulation elements when the time separation is equal to or exceeds the threshold; and 
 means for filtering the command when the time separation is less than the threshold. 
 
   
   
     18. The apparatus of  claim 14 , wherein the threshold is within a range of 1/4 of a chip in time to two chips in time.